JP2001121332A - Twist drill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a twist drill excellent in scrap discharge even when flow- out speed for thickened scraps in a sheared shape each such as a long pitch and a jigzag shape, is low. SOLUTION: Let the groove widths 3 and 3' of a twisting groove 2 provided for the outer circumference 1a of a twist drill 1 be gradually increased toward the groove rear end part 6 side from the tip end part 5 side of the drill. The increasing ratio of a groove width ratio to be indicated by the angular ratio θ1/θ2 of each angle θ1 and θ2' at the groove part of the twisting groove to each angle θ1 and dθ2 'at the land part of a land, shall be 1.2 to 2.6, and the twisting angle θ2 at the heel 9 side is made smaller with respect to the twisting angle β1 at the leading edge 8 side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drill having improved chip evacuation in drilling, and more particularly to a drill having a long chip without cutting, and a chip having a chip thickness of a shear type. The present invention relates to a twist drill suitable for, for example, a thick chip having a low chip discharge speed.

[0002]

2. Description of the Related Art Drilling proceeds while cutting in a hole machined by the drill until a predetermined hole depth is reached. Chips cut in the hole will be extruded by the screw effect due to the helical flute, the outflow velocity of the chip and the chip generated by the next generated chip, and will be discharged through the space created by the inner wall of the drill groove and the machined hole. Depending on the form of the chip, the chip may be constrained by the drill groove and the inner wall of the machined hole or may be clogged without being discharged by friction.

The form of chips in drilling varies depending on the material to be machined, the shape of the cutting edge of the drill, the torsion angle, cutting conditions, and the like. Chips such as conical helical or fan-shaped chips have low friction in the drill groove and have good dischargeability, but long-pitch and zig-zag shear chips and thick chips In the case of (1), the friction in the drill groove is large, and the outflow speed of the chip is low, so that the chip is easily clogged.

The twist groove of a twist drill used for general drilling has a constant groove width at the tip of the drill and a groove width at the rear of the drill, or the core thickness of the drill is increased from the tip of the drill to the rear of the drill to improve drill rigidity. In such a twist drill, the width of the groove becomes smaller at the rear of the drill, and the cross-sectional area of the twist groove becomes smaller at the rear of the drill. There is a problem that chip friction is large and chip clogging easily occurs. The details will be described below.

FIGS. 4 and 5 show an example of a conventional twist drill. As shown in FIG. 4, the torsion groove 12 provided on the outer periphery 11a of the twist drill 11 has a groove 12 having a concave cross section as shown in FIG. It is continuously processed until. The groove rear end portion 16 is provided with a cut-up portion 17 formed by a grindstone or a milling cutter for groove formation, and a handle portion 18 is provided. The groove width of the twist groove 12 is the drill tip 15
The groove width 13 in the cross section of the outer peripheral corner 20 and the groove width 13 in the rear part of the drill are constant, and the angle θ
_The groove width ratio θ ₁₁ / θ ₁₂ represented by the ratio of the angle θ ₁₂ between the land ₁₁ and the land 22 is kept constant.

[0006]

However, in such a configuration, a shear-type chip having a large chip thickness, such as a long-pitch type or a zigzag type, has a large friction in the torsion groove 12, Chip clogging is likely to occur due to the low chip outflow speed. As shown in FIGS. 4 and 5, the groove width 13 of the twist groove is changed from the front end 15 to the rear end 16 of the groove.
In a certain case, the chips generated by the cutting edge 19 must pass through a space 14 having a certain area formed by the groove 12 and the inner wall of the machined hole. There was a problem that resistance increased.

SUMMARY OF THE INVENTION In view of the above-mentioned problems of the prior art, it is an object of the present invention to provide a chip having a long chip thickness and a low chip discharge speed such as a long pitch type or a zigzag type. Another object of the present invention is to provide a twist drill having a twist groove having good chip dischargeability.

[0008]

For this reason, in the present invention, there is provided a twist drill in which the width of a torsion groove provided on the outer periphery of the twist drill is gradually increased from the front end side of the drill to the rear end side of the groove. The above problem was solved by providing. Since the width of the torsional groove gradually increases, and the chip discharge cross-sectional area gradually increases, chips generated one after another are discharged without being accumulated.

When the ratio of increase in the groove width ratio of the twisted groove which gradually increases from the drill tip to the groove rear end is less than 1.2, the discharge effect is small, and if it exceeds 2.6, the land width at the groove rear is small. Since it is small and lacks torsional rigidity and breakage etc. is likely to occur,
It is preferable that the increasing ratio of the groove width ratio of the twist groove be 1.2 to 2.6. The groove width ratio is determined by the angle θ of the groove of the twist groove.
The ratio of the angle θ ₂ between ₁ and the land portion of the land 22 (θ ₁ / θ ₂ )
It is.

The torsion groove width may be gradually increased on the leading edge side or the heel side, but the groove processing is difficult. Therefore, in the present invention, the torsion groove width can be gradually increased by making the torsion angle on the heel side smaller with respect to the torsion angle on the leading edge side and not the same on the leading edge side and the heel side. I made it. Conventionally, the grooving grindstone is divided once or twice or more, and the grooves on the leading edge side and the heel side are twisted with the same angle, but in the present invention, the leading edge side and the heel side are Since the twist groove processing in which the twist groove width gradually increases can be performed only by processing at different angles, the conventional twist groove processing machine can be used as it is. In addition, in addition to the case where the heart thickness is constant,
The present invention can be applied to the case where the thickness of the heart is gradually reduced. If the core thickness increases gradually, the rate of increase of the groove width ratio should be increased so that the sectional area gradually increases as a result.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1, FIG. 2, and FIG.
An embodiment of the present invention will be described based on FIG. FIG. 1 is a side view of a twist drill showing an embodiment of the present invention, FIG. 2 is a cross-sectional view of a tip portion taken along a line AA of FIG.
FIG. 3 is a cross-sectional view of the rear end portion of the groove at right angles to the BB line axis in FIG.
The twist groove 2 provided on the outer circumference 1a of the twist drill 1 of the present invention has a groove width 3 and a groove rear end cross section (BB cross section) in the outer peripheral corner 20 cross section (AA cross section) at the tip of the drill.
Is gradually increased from the drill tip 5 side toward the groove rear end 6 side. In the torsion groove 2, the groove 2 on the cross section is formed by the torsion angle β of the leading edge 8.
_1, the twist angle beta ₂ of the heel 9 than the helix angle beta ₁ small, are continuous from the distal end 5 of the drill at each constant twist angle to the groove rear end 6. Drill tip 5 at this time
The groove width ratio at the outer peripheral corner 20 is expressed as θ ₁ / θ ₂ , and the groove width ratio at the groove rear end 6 is expressed as θ ₁ ′ / θ ₂ ′, from the drill tip 5 side to the groove rear end 6 side. It is gradually increasing toward. 17 is a cut-out portion, 18 is a handle portion, 21 is a margin, 22 is a second cut surface, and 23 and 23 'are core thicknesses.

[0012]

Next, a cutting test of drilling by the drill according to the embodiment of the present invention and a conventional drill was performed.
The diameter of the conventional drill is 6 mm, the torsion angle β ₁₁ of the leading edge and the heel is 30 °, and the groove width ratio is 1.0.
This is a twist drill made of cemented carbide. The drill of the present invention is a twist drill made of cemented carbide and having a diameter of 6 mm as in the prior art, but the torsion angle β ₁ of the leading edge 18 is 30 ° and the torsion angle β ₂ of the heel 9 is 28 °. At this time, the outer peripheral corner 20 of the drill tip 5 is also used.
And the groove width ratio at the rear end of the groove is 1.5.
The core thickness is constant at 1.2 mm in both cases.

The cutting conditions were as follows. Cutting conditions Drill dimensions φ6 × 72 (total length) × 28 (groove length) Drill material Carbide Work material Aluminum alloy A5052 Hole depth 18mm blind hole Cutting speed 150m / min Feed amount 0.1mm / rev Cutting oil agent Dry This invention Table 3 shows the results of comparative measurement of the number of holes that can be drilled with one drill for each of three conventional products and the number of holes that can be drilled by one drill (the number of life-drilled holes).

[0014]

[Table 1]

As shown in Table 1, the chip of the conventional drill clogged in the groove, and the life of the drill was 12 holes in a small number, 55 holes in a large number, and an average of 33 holes. There was no chip clogging and all three could be machined with 1000 holes or more. In the above-described embodiment, the material of the drill is cemented carbide, but it goes without saying that the invention can be applied to a twist drill made of high-speed tool steel and further coated with a hard coating.

[0016]

As described above, in the present invention, the groove width of the twist groove is gradually increased from the tip end of the drill toward the rear end of the groove, and the chip discharge cross-sectional area in the groove width direction is gradually increased. Since the chips are made easier to discharge, it is possible to efficiently discharge chips such as long-pitch type and zigzag type chips that have a large chip thickness and a low chip outflow speed. . Further, the chip discharge performance is improved, so that chip clogging is less likely to occur and the drill life can be extended.

Further, since the increase ratio of the groove width ratio of the twist groove which gradually increases from the drill tip to the groove rear end is set to 1.2 to 2.6, the performance relating to the drill strength is increased by increasing the twist groove width. Etc. do not decrease.

Further, by reducing the torsion angle on the heel side with respect to the torsion angle on the leading edge side, the torsion groove whose torsion groove width gradually increases only by machining the leading edge side and the heel side at different angles. The twist drill can be machined, and the conventional twist groove machine can be used as it is, and the machining is simple, so that a low cost and good chip discharge twist drill can be provided.

[Brief description of the drawings]

FIG. 1 is a side view of a twist drill showing an embodiment of the present invention.

FIG. 2 is a cross-sectional view taken along the line AA of FIG. 1 showing a cross-section of an outer peripheral corner of a tip portion of the twist drill of the present invention.

FIG. 3 is a cross-sectional view taken along a line BB of FIG. 1 showing a cross-section of a rear end portion of the twist drill groove of the present invention.

FIG. 4 is a side view of a conventional twist drill.

FIG. 5 is a cross-sectional view taken along a line CC of FIG. 4 showing a cross section of an outer peripheral corner of a tip portion of a conventional twist drill.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Twist drill 1a Outer circumference 2, 2 'Twist groove 3, 3' Groove width 5 Drill tip 6 Groove rear end 8 Leading edge 9 Heel β ₁ Torsion angle on leading edge β ₂ Torsion angle on heel side θ ₁ , θ ₁ ′ Groove angle θ ₂ , θ ₂ ′ Land angle

Claims (3)

[Claims] 1. A twist drill characterized in that a groove width of a twist groove provided on an outer periphery of the twist drill gradually increases from a tip end side of the drill to a trailing end side of the groove. 2. The twist drill according to claim 1, wherein the increasing ratio of the groove width ratio of the twist groove gradually increasing from the drill tip to the groove rear end is 1.2 to 2.6. . 3. The twist angle of the twist groove provided on the outer periphery of the twist drill is such that the twist angle on the heel side is smaller than the twist angle on the leading edge side. Or the twist drill according to 2.